Electric heating devices



P 1957 A. c. BOGGS ETAL 2,807,696

ELECTRIC HEATING DEVICES Filed Jan. 7, 1953 Fig.1 7

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l a' l a INVENTORS HLBEM C. BOGGS w THOMHS M. ox 5 Hffbmey United StatesPatent Office 2,807,696 Patented Sept. 24, 1957 ELECTRIC HEATING DEVICESAlben C. Boggs and Thomas M. Fox, Pittsburgh, Pa., as-

signors to Edwin L. Wiegand Company, Pittsburgh, Pa", a corporation ofPennsylvania Application January 7, 1953, Serial No. 330,046

1 Claim. (Cl. 20167) My invention relates to electric heating devices,particu- V larly to such devices which are sealed against entrance ofdeleterious matter, and the principal object of my invention is toprovide new and improved devices of this character.

My invention is particularly adaptable for use with an electric heatingdevice of the sheathed type comprising a resistor and a sheath enclosingthe resistor, the latter being electrically insulated from the sheath bysuitable electrical-insulating, heat-conducting means. The inventionprovides means for sealing the ends of heating devices and also providesmeans for electrically connecting the heating device to a source ofelectrical current, the electrical connection between the terminal ofthe resistor and the conductor wire being adequately protected againstshorting and against action of deleterious matter which may be in closerelation to the device.

In this respect, the heating device is admirably suited for use wherehumidity or moisture conditions prevail, such as, for example, for useas a defroster element in refrigeration apparatus.

In the drawing accompanying this specification and forming a part ofthis application, there are shown, for purposes of illustration, severalembodiments which my invention may assume, and in this drawing:

Figure 1 is a broken elevational View of a heating device disclosing oneembodiment of my invention,

Figure 2 is a sectional view corresponding generally to the line 2-2 ofFigure 1,

Figure 3 is a broken elevational view of a heating device disclosinganother embodiment of my invention, and

Figure 4 is a sectional view corresponding generally to the line 4-4 ofFigure 2.

With particular reference to Figures 1 and 2 of the drawing, theembodiment of the invention therein disclosed comprises an electricresistance heater having a sheath 11, preferably of metal, and aresistor (not shown) electrically connected to a terminal pin 12.

Suitable refractory material 14 embeds the resistor and the inner end ofthe terminal pin 12 and serves both to electrically insulate theresistor and the pin and also to conduct heat from the resistor to thesheath. The refractory material stops short of, or is routed out from,an end of the sheath to form an opening 15, and the resistor terminalextends through such opening and outwardly of the sheath.

An apertured plug 16 is disposed about the terminal 12 and within theopening 15, and the plug may have a portion extending outwardly of theopening. As presently preferred, the sheath 11 is of a transverse size,at least adjacent the opening 15, so that the plug 16 may be insertedinto the opening without requiring a great amount of force. Thereafter,the sheath, at least adjacent the opening 15, is subjected to a swagingoperation so as to reduce its transverse size and thereby compress theplug 16 into sealing engagement with adjacent surfaces of the openingand the terminal 12.

In some cases the sheath is subjected to a swaging operation throughoutits active length in order to compress and adequately compact therefractory material, and in such cases the end of the sheath may besimultaneously swaged to effect sealing of the plug 16. It has beenfound that the swaged plug provides an adequate seal for the sheath notonly effective for subsequent forming operations on the sheath but alsoeffective generally throughout the life of the heating device, and thatthe plug prevents entrance of moisture and other deleterious matterwhich otherwise would impair the usefulness of the heat ing device.

The plug 16 may be formed of any suitable material which lends itself tothe compressive sealing action caused by swaging, and at present it ispreferred to form the plug of a suitable rubber material. As seen inFigure 2, an end of the terminal 12 extends beyond the outer end of theplug 16, for a purpose to appear.

An electrical conductor 17, securable in any suitable manner to a sourceof electrical current, is electrically connected to the terminal 12, andas herein disclosed, a tubular member 18, of electrical conductingmaterial, is formed to generally closely receive, in its opposite ends,the terminal 12 and the conductor 17, and the opposite ends of themember 18 are swaged or suitably indented, as shown at 19, toelectrically and mechanically bond the terminal and conductor to themember.

The conductor is provided with electrical insulation 20 and in thepresent embodiment such insulation is preferably a rubber material.

Electrical insulation 21 is disposed about the electrical connectionformed by the member 18 and such insulation is connected to the plug 16and the insulating covering 20 in sealing relation to protect theelectrical connection. In the present embodiment, it is preferred toform the insulation of rubber material and to mold it about theelectrical connection and vulcanize it to the plug 16 and to theinsulating covering 20.

As best seen in Figure 2, the insulation 21 spans the space between theopposed faces of the plug 16 and insulating covering 20 and isvulcanized to such faces. It is preferred that the transverse sizes ofthe plug 16, the insulating covering 20, and the insulation 21 do notmaterially exceed the transverse size of the sheath 11 and in theembodiment shown in Figure 2 the plug, insulating covering and theinsulation are of a diameter equal to, or slightly less than thediameter of the sheath so that the protective insulation at the end ofthe sheath will in elfect be a continuation of the sheath. Thus, bulkyprotective and insulating means are eliminated and the heating devicemay be used in constructions having space limitations.

It will be further appreciated that the lead from the sheath possessesflexibility and may be flexed to suit space limitations withoutsubjecting the heating device to deleterious infiltration of harmfulmatter. This is an important feature of the invention since devices usedin cases such as for refrigeration defrosting must be absolutely sealedto guarantee against harmful shorting of the electrical connection to apart of the refrigerator.

The embodiment of the invention shown in Figures 3 and 4 is similar tothat shown in Figures 1 and 2, and like parts are designated by likereference numerals supplemented by the suflix a. In this embodiment, theinsulation 21a is molded about the plug 16a to provide a tubular portion25 which is also vulcanized to the plug. Further, in this embodiment,the transverse size of the insulating covering 20a is less than thetransverse size of the insulation 21a and the latter is molded about andvulcanized to the covering 20a to enhance the sealing effect.

It will be appreciated that the material forming the :3 plug, insulationand insulating covering may be of a rubber to suit requirements, andthat natural or synthetic rubber, or rubber-like plastics, may be usedwhere conditions dictate.

In view of the foregoing it'will be apparent to those skilled in the artthat I have accomplished at least the principal object of my inventionand it will also be apparent to those skilled in the art that theembodiments herein described may be variously changed and modified,without departing from the spirit of the invention, and that theinvention is capable of uses and has advantages not herein specificallydescribed, hence it will be appreciated that the herein disclosedembodiment is illustrative only, and that my invention is not limitedthereto.

We claim:

An electric heating device, comprising an electric resistance heaterincluding a tubular metallic sheath enclosing a resistor terminal pinextending axially thereof and embedded in a surrounding heat conductingrefrac- 'tory material, said refractory material terminating short of anend of said sheath and partially defining an opening in said sheaththrough which said terminal pin projects axially outwardly therefrom, acylindrical deformable compressible plug of rubber material having itsinner end disposed in said sheath opening and surrounding the projectingend of said terminal pin, the end wall of said sheath surrounding saidopening being of contracted reduced diameter to exert pressure laterallyinwardly against the outer cylindrical wall of said plug to radiallycompress the plug and hold it in fixed sealing position against theinner surface of said sheath wall and to hold the plug material insealing engagement With the outer surface of said terminal pin, aconductor wire having an electrically insulating covering, said Wirehaving electrical connection with said terminal pin, and insulatingmeans disposed around said electrical connection, opposite ends of saidinsulating means being sealed to and respectively abutting against theouter end wall of said plug and the inner end of said insulatingcovering of said conductor Wire, said insulating means being of atransverse size not materially exceeding the transverse size of saidsheath.

References Cited in the file of this patent UNITED STATES PATENTS Re.23,679 Charbonneau et al. July 7, 1953 2,460,795 Warrick Feb. 1, 19492,490,934 Vogel Dec. 13, 1949 2,536,003 Dupre Dec. 26, 1950 2,538,808Swiss Jan. 23, 1951 2,659,795 Boggs Nov. 17, 1953 FOREIGN PATENTS557,765 Great Britain Dec. 3, 1943

